Pokemon X: Editing Trainer Class Music Association

[Isol8iv]

I'd like to change the battle music of certain Trainers who currently use the normal Trainer theme (Sycamore, for example, or one out of the four Team Flare scientists), and I believe that editing the "xy_sound.bcsar" file somehow is probably the way to do this. I've seen a video on how this kind of thing is done in Gen 3, but I'm working with Gen 6 here. I'm also a complete noob at hex editing. Does anyone know how I might be able to change the battle music associated with specific Trainer Classes with this file, or otherwise?

As a side note, I have edited this file before in order to change the loop points of a custom song I put into the game, which worked fine.

[Isol8iv]

The other way to achieve what I want would be to change what image appears when you start a battle with a certain Trainer Class. Then, for example, I could change some other Trainer's image that has different music to Sycamore's, then add a new track to replace the one associated with that class, which I know how to do.